August 17, 1882] 



NA TURE 



33; 



at the sea-level, a position favourable for air-, but not for sun- 

 warmth. In our large town?, however, we artificially create an 

 impenetrable barrier to solar radiation by throwing into the air 

 the imperfectly burnt products of bituminous coal. 



These products are of three kinds— soot, tar, and steam. 

 Every ton of bituminous coal burnt in our grates gives off about 

 6 cwts. of volatile but condensable products. The less perfect 

 the combustion the more tar and the less steam will be produced. 

 If perfectly burnt without any smoke, then about 9 cwts. of 

 steam, occupying 27,359 cubic feet at 100° C, or 20,024 cubic 

 feet at 0° C. will be sent into the air. Now, 33,333 tons of 

 bituminous coal are, on the average daily consumed in London 

 in winter, giving 667,460,000 cubic feet of steam at o° C. 



This combustion of enormous quantities of bituminous coal acts 

 in the production of town f g in three ways : — 1st. By supplying 

 the basis of all fog — condensed watery particles. 2nd. By deter- 

 mining the condensation of atmospheric moi ture in the form of 

 fog. 3rd. By coating the fog particles with tar, and thus making 

 them more persistent. 



All fogs have for their basis watery particles, and the greater 

 part even of the suspended matters visible in a ray of electric 

 light consists of these particles, for the air becomes nearly clear 

 when it is heated somewhat above 100° C. [Experiment shown]. 

 Everything therefore which increases the proportion of aqueous 

 vapour in town air tends to produce fog. But aqueous vapour 

 alone would 1 robably never produce fog, for it condenses at once 

 to large particles, which rapidly fall as rain. When, however, 

 solid or liquid particles are present in the air, the minute spherules 

 of fog are produced. This was first shown by Messrs. Coulier 

 and Mascart, in 1875, and their results have since been confirmed 

 by Mr. Aitkin. The speaker showed that air filtered through 

 cotton wool, though afterwards saturated with moisture, produced 

 no fog when its temperature was lowered ; but as soon as a small 

 quantity of the dusty air of the theatre was admitted fog was 

 immediately formed, whilst, when a little coal smoke was intro- 

 duced, a dense and more persistent fog was the result. 



The fog once formed is rendered more persistent by the coating 

 of tarry matter which it receives from the products of the imper- 

 fect combustion of smoky coal. The speakerhadmadenumerous 

 experiments on the retardation of evaporation by films of coal tar. 

 He had found that the evaporation of water in a platinum dish 

 placed in a strong draught of air was retarded in one experiment 

 by 84 per cent, and in another by 78 '6 per cent., when a thin 

 film of coal tar was placed on the surfaces. Even by the mere 

 blowing of coal smoke on the surface of the water for a few 

 seconds, the evaporation was retarded by from 77*3 to 81*5 per 

 cent. Dro| s of water suspended in loops of platinum wire were 

 also found to have their evaporation retarded by coal smoke. 

 Hence arise the so-called dry fogs which have been observed by 

 Mr. Glaisher in balloon ascents, some examples of which are 

 given in the following table : — 



Fog in comparatively Dry Air. 

 Place of Ascent. 



Wolverhampton 



Crystal Palace... 



Wolverton 

 Woolwich 



Thus the smoke of our domestic fires constitutes a potent cause 

 both for the generation and the persistency of town fogs. In 

 London, at all events, if all manufacturing operations were 

 absolutely to cease, the fogs would not be perceptibly less dense 

 or irritating. Granting then this cause of town fogs, what are the 

 remedies open to us? The speaker was of opinion that the 

 substitution of a sufficient number of smoke-consuming grates 

 (assuming a smoke-consuming grate to have been invented), for 

 the 1,800,000 fire-places of London was quite hopeless, and that 

 one remedy only could be of any appreciable service — the importa- 

 tion of bituminous coal must be forbidden. This is a case in which 

 individual effort can do nothing; but State or municipal action 

 would be simple and decisive. 



There need be no fear that the price of smokeless fuel would 

 rise inordinately, for the sources of this fuel are too numerous 

 and inexhaustible to admit of either a monopoly or a serious rise 



in price. In addition to the enormous stores of smokeless coal 

 in the Welsh coal-fields, every bituminous coal yields a smokeless 

 coke, either in the retorts of gasworks or in coke ovens. On the 

 average, 100 tons of smoky coal yields 60 tons of coke, the re- 

 maining 40 tons being driven off as combustible gas, ammoniacal 

 liquor and tar ; and as there is an almost unlimited demand for 

 these products, it is not unlikely that they would, under the 

 circumstances contemplated, repay the cost of coking, and it 

 is worthy of note that coal of very inferior quality makes fairly 

 good coke. 



The only objection to the domestic use of smokeless coal and 

 coke is the difficulty of lighting the fire, but this is obviated by 

 the use of gas as proposed by Dr. Siemens. In ordinary grates, 

 however, there is little difficulty in lighting and burning these 

 smokeless fuels if the throat of the chimney be contracted so as 

 to increase the draught. In this way nearly every grate in 

 London could be rendered sn okeless at an expenditure of a 

 couple of shillings. 



It is unnecessary to enumerate the many advantages of a 

 smokeless atmosphere, but it may here be mentioned that London 

 fogs not only seriously injure health but annually destroy the lives 

 of thousands. In one week alone upwards of 1, 100 lives have 

 been thus sacrificed in Londi n. We have doubtless still long to 

 wail before the only remedy for London fogs will be adopted ; 

 but in the meantime, immunity from their effects, so far as the 

 respiratory organs are concerned, may be obtained by the use of 

 a small and very portable cotton-wool respirator which is made, 

 in accordance with the speaker's directions, by Mr. Casella, of 

 Holb rn. [Respirator exhibited.] Armed with this little in- 

 strument, he had often pas ed through the densest and most 

 irritating fogs with perfect immunity, breathing, in fact, all the 

 time, air even purer than that of the country. Such a remedy is, 

 however, obviously of extremely limited application. 



In conclusion he said, though we may, with justice, complain 

 of the scanty share of sunshine now received by us, let us not 

 forget that, in our coal-fields, we are compensated by vat stores 

 of the sunlight of past ages. How far through electricity, the e 

 stores can be evoked to supplement the present defective supply, 

 he would be a bold man who would venture to predict. Let us 

 not, however, continue to use this great legacy of light of the 

 past to obscure the small one of the piesent. 



SCIENTIFIC SERIALS 



American Journal of Science, July. — Contributions to meteoro. 

 logy (seventeenth paper), by E. Loomis. — The phenomena of 

 metalliferous vein-formation now in progress at Sulphur Bank, 

 California, by J. Le Conte and W. B. Ri-ing. — Modes of occur- 

 rence of the diamond in Brazil, by O. A. Derby. — On the influ- 

 ence of time on the change in the resistance of the carbon-disc 

 of Edison's tasimeter, by T. C. Mendenhall. — Further observa- 

 tions on the crystallised sands of the Potsdam sandstone of 

 Wisconsin, by A. A. Young.— On the origin of jointed 

 structure, by G. K. Gilbert. — Break-circuit arrangements for 

 transmitting clock-beats, by F. E. Nipher. — Cirriped crustacean 

 from the Devonian, by J. M. Clarke. 



Archives des Sciences Physiques et NaturcUcs, No. 7, June 15. 

 — Contribution of astronomy to the solution of a problem of 

 molecular physics, by M. R. Pictet. — Study of the variations of 

 kinetic energy of the solar system, by MM. Pictet and Cellerier. 

 Swiss Committee of Geological Unification, by M. Renevier. — 

 On a characteristic of the Batatas, whose singularity in the family 

 of the Convolvulaceje has not been sufficiently remarked, by M. 

 de Candolle.— Observation of Mr. Meehan on the variability of 

 the English oak (Qucrcus robur), and remark by M. de Candolle. 

 — Note on Echinida gathered in the environs of Camerino 

 (Tuscany), by M. Canavari. 



No. 7, July 15 — On the rotatory polarisation of quartz, by 

 MM. Soret and Sarasin. — On the diffusion of bacteria, by M. 

 Schnetzler. — Petrogenic classification or grouping of rocks 

 according to their vnor'e of formation, adopted for academic 

 instruction and for the museum of Lausanne, by M. Renevier. 



SOCIETIES AND ACADEMIES 



Vienna 

 Imperial Academy of Sciences, July 13. — O. Tumlirz, 

 on a method for researches on the absorption of light by 



